Disabled escaping of single quote since it is valid for JSON (though invalid for JavaScript).

Added null checks in contexts since the custom type adapter can pass nulls.

gson/src/main/java/com/google/gson/Escaper.java

@@ -54,8 +54,10 @@ class Escaper {
     htmlEscapeSet.add('>');
     htmlEscapeSet.add('&');
     htmlEscapeSet.add('=');
-    htmlEscapeSet.add('\'');
- //   htmlEscapeSet.add('/');  -- Removing slash for now since it causes some incompatibilities
+    // Removing ' for now since it is a valid character in JSON, but not javascript
+    // When enabling this, remember to enable the test EscaperTest.disable_testSingleQuoteEscaping
+//    htmlEscapeSet.add('\''); 
+//    htmlEscapeSet.add('/');  -- Removing slash for now since it causes some incompatibilities
     HTML_ESCAPE_CHARS = Collections.unmodifiableSet(htmlEscapeSet);
   }
 

gson/src/main/java/com/google/gson/JsonDeserializationContextDefault.java

@@ -43,14 +43,14 @@ final class JsonDeserializationContextDefault implements JsonDeserializationCont
 
   @SuppressWarnings("unchecked")
   public <T> T deserialize(JsonElement json, Type typeOfT) throws JsonParseException {
-    if (json.isJsonArray()) {
+    if (json == null || json.isJsonNull()) {
+      return null;
+    } else if (json.isJsonArray()) {
       return (T) fromJsonArray(typeOfT, json.getAsJsonArray(), this);
     } else if (json.isJsonObject()) {
       return (T) fromJsonObject(typeOfT, json.getAsJsonObject(), this);
     } else if (json.isJsonPrimitive()) {
       return (T) fromJsonPrimitive(typeOfT, json.getAsJsonPrimitive(), this);
-    } else if (json.isJsonNull()) {
-      return null;
     } else {
       throw new JsonParseException("Failed parsing JSON source: " + json + " to Json");
     }

gson/src/main/java/com/google/gson/JsonSerializationContextDefault.java

@@ -39,6 +39,9 @@ final class JsonSerializationContextDefault implements JsonSerializationContext
   }
 
   public JsonElement serialize(Object src) {
+    if (src == null) {
+      return JsonNull.createJsonNull();
+    }
     return serialize(src, src.getClass());
   }
 

gson/src/test/java/com/google/gson/EscaperTest.java

@@ -65,7 +65,7 @@ public class EscaperTest extends TestCase {
     assertEquals("123\\\"456", escapedString);
   }
   
-  public void testSingleQuoteEscaping() throws Exception {
+  public void disable_testSingleQuoteEscaping() throws Exception {
     String containsQuote = "123'456";
     String escapedString = escapeHtmlChar.escapeJsonString(containsQuote);
     assertEquals("123\\'456", escapedString);

gson/src/test/java/com/google/gson/functional/NullObjectAndFieldTest.java

@@ -21,6 +21,8 @@ import com.google.gson.GsonBuilder;
 import com.google.gson.JsonElement;
 import com.google.gson.JsonNull;
 import com.google.gson.JsonObject;
+import com.google.gson.JsonDeserializationContext;
+import com.google.gson.JsonDeserializer;
 import com.google.gson.JsonSerializationContext;
 import com.google.gson.JsonSerializer;
 import com.google.gson.common.TestTypes.BagOfPrimitives;
@@ -173,7 +175,34 @@ public class NullObjectAndFieldTest extends TestCase {
     ObjectWithField obj = gson.fromJson(json, ObjectWithField.class);
     assertNull(obj.value);    
   }
-  
+
+  public void testCustomTypeAdapterPassesNullSerialization() {
+    Gson gson = new GsonBuilder()
+        .registerTypeAdapter(ObjectWithField.class, new JsonSerializer<ObjectWithField>() {
+          public JsonElement serialize(ObjectWithField src, Type typeOfSrc,
+              JsonSerializationContext context) {
+            return context.serialize(null);
+          }
+        }).create();
+    ObjectWithField target = new ObjectWithField();
+    target.value = "value1";
+    String json = gson.toJson(target);
+    assertFalse(json.contains("value1"));
+  }
+
+  public void testCustomTypeAdapterPassesNullDesrialization() {
+    Gson gson = new GsonBuilder()
+        .registerTypeAdapter(ObjectWithField.class, new JsonDeserializer<ObjectWithField>() {
+          public ObjectWithField deserialize(JsonElement json, Type type,
+              JsonDeserializationContext context) {
+            return context.deserialize(null, type);
+          }
+        }).create();
+    String json = "{value:'value1'}";
+    ObjectWithField target = gson.fromJson(json, ObjectWithField.class);
+    assertFalse("value1".equals(target.value));
+  }
+
   private static class ObjectWithField {
     String value = "";
   }